Method and apparatus for external intermediate data processing

ABSTRACT

Disclosed is a system for selectively enabling intermediate data processing of digital signals external to an integrated circuit (IC). The system comprises a transcoder, a codec connected to the transcoder, and a data processor located externally to the IC. In response to a strobe signal, a programmable switch diverts digital signals between the transcoder and the codec to a data path from the IC to the external processor. The digital signals are formatted within the IC for processing by the external processor. The externally processed digital signals are returned to the IC via a data path from the external processor. The digital signals are then reformatted within the IC for further processing by the IC.

This application is a continuation of Ser. No. 08/668,600 filed Jun. 18, 1996 U.S. Pat. No. 5,657,351 which is a continuation Ser. No. 08/192,057 filed Feb. 4, 1994 now abandoned.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to the following U.S. Patent Applications:

    ______________________________________                                         Ser. No.   TITLE            INVENTOR(S)                                        ______________________________________                                         07/917,497 General I/O Port Inter-                                                                         Gulick, et                                                    rupt Mechanism   al.                                                07/917,489 Improved External Memory                                                                        Gulick, et                                                    Access Control for a                                                                            al.                                                           Processing Unit                                                     07/917,488 Method of Weak Pull-up                                                                          Bowles, et                                                    Disable and Mechanism                                                                           al.                                                           Therefor for Use with                                                          Microcontroller in Inte-                                                       grated Circuit and Cord-                                                       less Telephone Using the                                                       Integrated Circuit                                                  07/917,503 Interrupt Mask Disable                                                                          Bowles, et                                                    Circuit and Method                                                                              al.                                                07/918,627 Integrated Circuit and                                                                          Gulick, et                                                    Cordless Telephone Using                                                                        al.                                                           the Integrated Circuit                                              07/918,626 Modulator Test System                                                                           Peterson, et                                                                   al.                                                07/918,625 Keypad Scanner Process                                                                          Gulick                                                        and Device and Cordless                                                        Telephone Employing the                                                        Mechanism                                                           07/918,624 Serial Interface Module                                                                         Gulick, et                                                    and Method       al.                                                07/918,631 Low Power Emergency Tele-                                                                       Peterson, et                                                  phone Mode       al.                                                07/918,632 In-Circuit Emulation                                                                            Gulick, et                                                    Capability Mode in Inte-                                                                        al.                                                           grated Circuit and Cord-                                                       less Telephone Using the                                                       Integrated Circuit                                                  07/918,622 Clock Generator Capable                                                                         Peterson, et                                                  of Shut-down Mode and                                                                           al.                                                           Clock Generation Method                                             07/918,621 Signal Averager  Gulick                                             08/192,007 Power Management Circuit                                                                        Hendrickson,                                                  for Use in Digital Cord-                                                                        et al.                                                        less Telephones and Like                                                       Apparatus                                                           08/191,949 Apparatus and Method for                                                                        Schnizlein,                                                   Sending Signal Data                                                                             et al.                                             08/191,940 Burst Synchronization of                                                                        Schnizlein                                                    Time Division Multiplexed                                                      Transceiver Pairs                                                   08/191,944 Receiver Quality Measure-                                                                       Hendrickson,                                                  ment System for Use in                                                                          et al.                                                        Digital Cordless Tele-                                                         phones and Like Apparatus                                           08/192,046 Dual-Mode Baseband Con-                                                                         Hendrickson,                                                  troller for Radio-Fre-                                                                          et al.                                                        quency Interfaces Relat-                                                       ing to Digital Cordless                                                        Telephones                                                          08/192,009 Metal Programmed Transis-                                                                       Allee                                                         tor Array                                                           08/191,948 Input/Output Data Port                                                                          Mullins, et                                                   and Method       al.                                                08/191,818 Method and Aparatus for                                                                         Hendrickson                                                   Improved Link Establish-                                                       ment and Monitoring in a                                                       Communications System                                               ______________________________________                                    

All of the related applications are assigned to the assignee of the present invention and are hereby incorporated herein in their entirety by this reference thereto.

BACKGROUND

1. Field of the Invention

The present invention relates to telecommunication controllers (i.e., IC) and, more particularly, external intermediate data processing for such controllers.

2. History of the Related Art

The cordless telephone industry is currently in a state of expansion and transition. Several cordless telephone system standards have been previously developed. Currently these existing standards collectively require different types of data processing.

Additionally, new system standards for data processing are required by various countries to contend with the expansion of the cordless telephone industry. One standard, Cordless Telephony Generation 2 (CT2) interface specification for digital technology, is currently widely followed in the United Kingdom and certain European countries. The CT2 standard has been accepted by the European Telecommunications Standard Institute (ETSI) as an interim European standard. Unfortunately, not all countries have adopted the same standard. For example, the U.S. follows a standard that is different than the CT2 standard.

Current cordless telephone controllers utilized by the telecommunication industry, such is, for example, Am79C410 controller (i.e., IC) manufactured by Advanced Micro Devices (AMD), perform data processing internally. Since the data processing is internal, the controller must be redesigned each time requirements or standards change so that the data processing complies with the new specifications and standards. Redesign and fabrication of new controllers is expensive and time consuming. Furthermore, fabrication lot sizes must be carefully calculated to avoid creating an excess inventory of outdated controllers.

It would be a distinct advantage to have a controller which is not heavily dependent upon an internal data processing capability. If the controller's data processing could be upgraded without redesigning and fabricating a new controller, larger quantities of controllers could be manufactured, thereby achieving lower unit costs. Furthermore, the data processing capability of the controller could be upgraded more frequently to meet ever-changing specifications and standards. Providing a controller with a design that is not heavily dependent upon an internal data processing capability eliminates the need to design a new controller for each new data processing implementation. The present invention provides a controller with these advantages.

SUMMARY

In certain embodiments, the present invention includes methods and systems for external data processing. In one such embodiment, the invention is a system for selectively enabling intermediate data processing of digital signals external to an integrated circuit (IC). The system includes a transcoder and a codec connected to the transcoder. The system further includes a data processor located externally to the IC. Additionally, the system includes means for selectively diverting the digital signals, transmitted between the transcoder and the codec, to the external data processor for external processing of the digital signals. The system further includes means for returning the externally processed digital signals to the IC.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will be better understood and its numerous objects and advantages will become more apparent to those skilled in the art by reference to the following drawings, in conjunction with the accompanying specification, in which:

FIG. 1 is a block diagram of a controller for a digital cordless handset and base station utilizing the preferred embodiment of the present invention;

FIG. 2. (PRIOR ART) is a block diagram illustrating an Adaptive Differential Pulse Code Modulation (ADPCM) coder/decoder (codec) of an exemplary prior version of a controller;

FIG. 3 is a block diagram illustrating a transcoder and a codec which reflect the ADPCM codec of FIG. 2 of the preferred embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating the transcoder and codec of FIG. 3 in more detail in the preferred embodiment of the present invention; and

FIG. 5 is a timing diagram illustrating timing sequences utilized for intermediate data processing that may be employed in the transcoder and codec of FIG. 4 in the preferred embodiment of the present invention.

DETAILED DESCRIPTION

The preferred embodiment of the present invention may be implemented in a controller 10 as illustrated in FIG. 1. The controller 10 may be, for example, the Am79C410A CT2 manufactured by Advanced Micro Devices (AMD). An earlier version of the controller 10 (Am79C410) is described in more detail in co-pending U.S. patent application Ser. No. 07/918,627 and titled "INTEGRATED CIRCUIT AND CORDLESS TELEPHONE USING THE INTEGRATED CIRCUIT" and filed Jul. 21, 1992 by Gulick, et al., which is incorporated herein by reference.

Referring to FIG. 1, a controller for data processing is indicated generally at 10. The controller may be, for example, the Am79C410A CT2 controller or some other controller. The controller generally includes a transcoder 102 and a codec 101.

Referring now to FIG. 2, an exemplary prior version of a controller 20 is illustrated, which controller includes an ADPCM codec device 84. Adaptive Differential Pulse Code Modulation (ADPCM) is a speech coding method which calculates the difference between two consecutive speech samples in standard PCM coded telecom voice signals. A coder/decoder (codec) converts a digital signal to an analog signal, and an analog signal to a digital signal. The ADPCM codec 84 at FIG. 2 generally includes an ADPCM input 86, an ADPCM output 88, a codec input 92 and a codec output 90. The ADPCM output 88 and ADPCM input 86 communicate with an audio multiplexer 116. A multiplexer is an electronic circuit which allows two or more signals to proceed over one communications circuit. The audio multiplexer 116 transmits signals to and from a Public Switched Telephone Network (PSTN) interface 114 and to and from a microphone/speaker 112.

Still referring to FIG. 2, a CT2 Common Air Interface (CAI) 109 receives the codec output 90 and transmits a signal for codec input 92. The CT2 CAI 109 performs CT2 formatting for a radio frequency (RF) transceiver 117 which includes an antenna 118. The controller 10 also provides a PCM clock signal (PCMCLK) 108 for use by external circuitry. The ADPCM codec 84 performs all data processing internally and does not provide access for external intermediate data processing.

Referring now to FIG. 3, according to the preferred embodiment of the present invention, the ADPCM codec 84 is replaced by a transcoder 102 and a codec 101 as illustrated in FIG. 3. This embodiment of FIG. 3 further illustrates how digital signals transmitted between the transcoder 102 and the codec 101 are diverted for external intermediate data processing. The controller 10 also provides an 8 kHz. clock signal (CLK8K) 110, the PCMCLK signal 108 and a Strobe 106, for use by external circuitry. The physical separation of the transcoder 102 and codec 101, within the controller, provides the capability for external intermediate data processing by external circuitry, such as, for example, an external DSP 130.

Further referring to FIG. 3, external intermediate data processing in the preferred embodiment is implemented by providing the capability to divert digital signals which are transmitted between the transcoder 102 and codec 101. The transmitted digital signals are diverted by utilizing a programmable switch 94. If the programmable switch 94 is closed, all processing of digital signals is performed internally within the controller 10. However, if the programmable switch 94 is open, digital signals between the transcoder 102 and the codec 101 are diverted to the external DSP 130 for external intermediate data processing. A diverted digital signal from either the transcoder 102 or the codec 101 is accessed by external circuitry through the utilization of multiplexed pin A3 (PCMOUT) at 103. Once the external circuitry has performed the appropriate data processing, the processed digital signal is reinserted into the controller 10 through the utilization of multiplexed pin A2 (PCMIN) at 104.

Still referring to FIG. 3, external intermediate data processing in the preferred embodiment allows the implementation of external circuitry for features such as security/encryption, intercom, or handset hands-free only operations. The external intermediate data processing enables the implementation of new data processing features without the requirement that a new controller be created for each new or different data processing concept.

Now referring to FIG. 4, a schematic representation of the codec 101 and the transcoder 102 of the preferred embodiment of the invention is illustrated in greater detail. In the embodiment, the transcoder 102 supports processing of PCM and digital streams. Pulse Code Modulation (PCM) is the most common method of encoding an analog voice signal into a digital bit stream. First, the amplitude of the voice conversation is sampled in a procedure Pulse Amplitude Modulation (PAM). The amplitude is then coded (quantized) into a binary (digital) number (i.e., zeros and ones). Adaptive Differential Pulse Code Modulation (ADPCM) is a speech coding method which calculates the difference between two consecutive speech samples in standard PCM coded telecom voice signals. The transcoder 102 supports the following formats for the PCM digital signal stream: A-law, μ-law and linear.

Still referring to FIG. 4, the transcoder 102 of the preferred embodiment is comprised of the following: an ADPCM decoder 206, a noise suppressor 208, an Rx (receive) Attenuator 210, a first summation device 212, a tone generator 214, a Tx (transmit) attenuator 228, a second summation device 230, an ADPCM encoder 232, an A/μ-law PCM decoder 236, an A/μ-law PCM encoder 234, an A/μ-law/linear PCM decoder 238, an A/μ-law/linear PCM encoder 242, a transcoder input port path 246, a transcoder output port path 250, an ADPCM to A/μ-law path 254, an A/μ-law to ADPCM path 256 and a loopback 2 258.

Continuing to refer to FIG. 4, in the preferred embodiment, the codec 101 performs the necessary operations for converting a digital signal to an analog signal, and an analog signal to a digital signal. The codec of the embodiment is comprised of the following: a low pass filter (LPF) 216, an interpolator 218, a D/A converter 220, a linear PCM encoder 244, an A/D converter 222, a Decimator 224, a high pass filter (Hpf), low pass filter (Lpf), direct current (DC) rejector 226, a linear PCM encoder 240, a codes output port path 248 and a codec input path 252.

Still referring to FIG. 4, the transcoder 102 of the preferred embodiment receives digital signal data streams in the following formats: 32 kilobytes per second (kbps) ADPCM, and 64 kbps operating at 512 Hertz (Hz) A-law, μ-law, and 128 kbps linear PCM. The 32-kbps ADPCM digital signal stream is in ADPCM format and is received by the ADPCM decoder 206 which converts the ADPCM data stream into a linear digital signal format (digital signal). The 64-kbps data stream must be in either A-law or μ-law PCM format and is received by the A/μ-law PCM decoder 236, which converts the received data stream into a linear digital signal format (digital signal). The digital signal from the ADPCM decoder 206 is received by the noise suppressor 208 and Rx (received) attenuator 210. The noise suppressor 208 analyzes the digital signal and outputs an appropriate signal to mute the digital signal if it is not human speech (i.e., noise). The digital signal from the A/μ-law PCM decoder 236 is also received by the Rx attenuator 210. The Rx attenuator 210 attenuates the received digital signal by creating a certain amount of loss to the digital signal's amplitude. The Rx attenuator 210 is programmable and is affected by the noise suppressor 208. A summing device 212 performs summing of a tone generated by the tone generator 214 and the received digital signal from the Rx attenuator 210. The output from the summing device 212 is a voice plus tone digital signal and is received by either the low pass filter 216, or the A/μ-law/linear PCM encoder 242 (via transcoder output port path 250). The low pass filter 216 manipulates the shape of the digital signal spectrum before digital-to-analog conversion of the digital signal. The output from the low pass filter 216 is received by the interpolator 218. The interpolator 218 increases the sampling rate to a higher frequency so that improved resolution is achieved during the digital-to-analog conversion of the digital signal. The output from the interpolator 218 is received by D/A convertor 220 which converts the digital signal to an analog wave form representation.

Still referring to FIG. 4, in the preferred embodiment, an analog waveform is received by the A/D convertor 222 and converted to a linear digital signal representation (digital signal). The digital signal is received by Decimator 224 which decreases the sampling rate of the digital signal to about 32 kilohertz (kHz). The output from the Decimator 224 is received by the Hpf, Lpf and DC rejector 226. The high pass filter within block 226 cuts the frequency off at about 3.9 kilohertz (kHz), and the low pass filter within block 226 cuts the frequency off at about 60 hertz (for A/C type interference). The DC rejector within block 226 removes any DC offset. The output from the Hpf, Lpf and Dc rejector 226 is received by Tx (transmit) attenuator 228 (Tx) or the linear PCM encoder 240 (via codec output port path 248). The Tx attenuator 228 provides gain control for the digital signal and is programmable. The output from the Tx attenuator 228 is received by a summing device 230. The summing device 230 slums the digital signal from the tone generator 214 with the received digital signal from the Tx attenuator 228. The output signal from the summing device 230 is received by the ADPCM encoder 232, the A/μ-law PCM encoder 234 or the Rx attenuator 210 (via loopback 2 at 258). The ADPCM encoder 232 converts the digital signal into ADPCM format operating at 32 kbps. The A/μ-law PCM encoder 234 converts the digital signal into either A-law or μ-law PCM format operating at 64 kbps with a frequency of 512 khz. The ADPCM to A/μ-law path 254 provides the capability to convert a digital signal from the ADPCM decoder 206 into either an A-law or μ-law PCM format operating at 64 kbps with a frequency of 512 khz. The A/μ-law to ADPCM path 256 provides the capability to convert a digital signal from the A/μ-law PCM decoder 234 into an ADPCM signal operating at 32 kbps.

Further referring to FIG. 4, intermediate data processing of the digital signal by external circuitry is implemented in the preferred embodiment by connection to port paths 250 and 246 of the transcoder 102 and port paths 252 and 248 of the codec 101.

Continuing to refer to FIG. 4, the codec output port path 248 of the preferred embodiment allows the diversion of the digital signal before the transcoder 102 for external data processing. The codec output port path 248 is provided with a linear PCM encoder 240 which receives the diverted digital signal and converts it to a linear PCM format. Once the external processing of the digital signal has been accomplished the processed digital signal is inserted via transcoder input port path 246. However, the processed digital signal must be in one of the following formats. A-law, μ-law or linear PCM. The transcoder input port path 246 accesses the transcoder 102 before the Tx attenuator 228 and is provided with an A/μ-law/linear PCM decoder 238, which converts the processed digital signal into a linear digital signal for the Tx attenuator 228.

Still referring to FIG. 4, the transcoder output port path 250 of the preferred embodiment allows the diversion of the digital signal before the codec 101 for external data processing. The transcoder output port path 250 is provided with an A/μ-law/linear PCM encoder 242 which converts the digital signal to either A-law, μ-law or linear PCM format. Once the external processing of the diverted digital signal has been accomplished the processed digital signal is inserted via codec input port path 252. However, the processed digital signal must be in linear PCM format. The codec input port path 252 accesses the codec 101 before the Lpf 216, and is provided with a linear PCM encoder 244 which converts the processed digital signal into a linear digital signal for the Lpf 216.

Now referring to FIG. 5, the preferred embodiment of interface timing for external processing of the diverted digital signals from the transcoder 102 and the codec 101 is illustrated. In the embodiment, the internal 8-kHz frame synchronization clock signal 110 (CLK8K) is phase-locked to an input 500-Hz. CT2 frame sync, so that the rising edge of the internal CLK8K signal corresponds to the 500-Hz transitions. As was shown in FIG. 3, pin BDP3₋₋ OUT5 132 transmits the CLK8K signal 110 to external circuitry such as the DSP 130. The Bit Data Multiplex (BDMUX) register, bits 6:5!, are utilized for this purpose.

Still referring to FIG. 5, the interface timing between the external circuitry, for example, an external DSP 130, and the controller may be coordinated in the preferred embodiment by strobe output 106. In that event, strobe output 106 may produce four pulses (TS0-TS3) during a single frame of the CLK8K signal 110 and is provided on pin A5. The first and third strobe pulses, TS0 and TS2, may be utilized by external circuitry for the receipt and transfer of a digital signal from the port paths of either the transcoder 102 or the codec 101. In this arrangement, if the strobe output 106 is active during the first strobe pulse (TSO), the external circuitry may interface with the codec port paths 248 and 252, and/or if the strobe output 106 is active during the third strobe pulse (TS2), the external circuitry may interface with the transcoder port paths 246 and 250. The defining of the two strobe pulses in this instance may be required, since port paths for the transcoder and the codec are multiplexed (via pin A3 (PCMOUT) 103 and pin A2 (PCMOUT) 104). Further in the arrangement, the other two pulses, TS1 and TS3, may be utilized by external circuitry acting as a slave to the controller.

Still referring to FIG. 5, in the preferred embodiment, a register strobe enable (STROBEN) may be provided in the controller to enable and disable the four pulses that may be, as described, associated with the strobe output. The register STROBEN in such instance may be defined as indicated below.

Register: STROBEN

Address: FF2A

    ______________________________________                                         Bit      Definition                                                            ______________________________________                                         3        Time slot 3 enable (last quadrant of 8 kHz frame).                              0: =disable, 1: =enable.                                             2        Time slot 2 enable (third quadrant of 8 kHz frame).                             0: =disable, 1: =enable.                                             1        Time slot 1 enable (second quadrant of 8 kHz frame).                            0: =disable, 1: =enable.                                             0        Time slot 0 enable (first quadrant of 8 kHz frame).                             0: =disable, 1: =enable.                                             ______________________________________                                    

Still referring to FIG. 5, in the preferred embodiment, a DSPCTR register of the controller may have bits which are defined as indicated below.

    ______________________________________                                         Bit  Definition                                                                ______________________________________                                         4: 3 Reserved                                                                  2: 0:                                                                               Codec Path Configuration                                                  A0 pin undriven at reset (A7-A0 pins used as address                           latch (default):                                                               000:   Normal ADPCM Codec configuration (ADPCM-Analog)                         001:   PCM Codec Configuration                                                        (A-law PCM at SDIN and SDOUT pins-Analog)                               010:   Loop 2 (Analog-Analog)                                                  100:   ADPCM Transcoder Configuration                                                 (A-law PCM at SDIN and SDOUT pins-ADPCM)                                A0 pin driven to 0 at reset (A7-A0 pins redefined to be                        serial voice I/O)                                                              000:   Normal (ADPCM-Analog)                                                   001:   Linear DSP Port for Hands-Free/Echo                                            Cancellation                                                                   (ADPCM-Linear PCM on A5-A2, Linear PCM on A5-                                  A2-Analog)                                                              010:   Loop 2 (Analog-Analog)                                                  100:   Reserved                                                                ______________________________________                                    

Further referring to FIG. 5, in the preferred embodiment, the STROBEN Register of the controller may be defined as indicated below.

4 Bypass Attenuators

1: Allow TXATTN and RXATTN attenuators to attenuate signals and allow injection of dual tore signals, if appropriately programmed.

0: Signals bypass the TXATTN and RXATTN attenuators and the dual tone generator is disabled. This configuration allows the controller to perform ADPCM-PCM transcoding functions with bit-for-bit compliance to CCITT G. 721 using the test sequences recommended by CCITT.

3:0: Codec Path Configuration

1001: Linear Port ADPCM-Linear PCM on pins 59-62)

0100: A-law ADPCM Transcoder Configuration (ADPCM-A-Law PCM on pins 58-62)

1100: μ-law ADPCM Transcoder Configuration (ADPCM-μ-law PCM on pins 58-62)

Still referring to FIG. 5, access to the transcoder and codec paths in the preferred embodiment is provided by utilizing and redefining port 0's multiplexed address/data pins 0-7. In the embodiment, the status of pin A0 of the port 0's multiplexed address pins controls whether pins A1 through A7 are redefined for external data processing. The status of pin A0 is determined at the end of reset. If A0 is not externally driven low, the latched address port 0 will operate normally as an 8-bit address output port. If A0 is externally driven low, the address port drivers are disabled and the port is redefined as illustrated below.

    ______________________________________                                                           A0 = 0 at reset                                                                             A0 = 0 at reset                                       A0 = undriven                                                                              and DSPCTR 2:0! =                                                                           and DSPCTR 2:0! =                               Pin   (default)   001 or 100   001                                             ______________________________________                                         ALE   CLK4M output or                                                                            ALE Output or                                                                               ALE output or                                   CLK4M ALE output or                                                                              ALE input    ALE input                                             ALE input                                                                A7    Address 7 output                                                                           CLK4M output CLK4M output                                    A6    Address 6 output                                                                           Reserved. Do not                                                                            Reserved. Do                                                      connect.     not connect                                     A5    Address 5 output                                                                           High (weak int                                                                              STROBE output                                                     pull-up)                                                     A4    Address 4 output                                                                           High (weak int                                                                              PCMCLK output                                                     pull-up)                                                     A3    Address 3 output                                                                           High (weak int                                                                              TDMed TX/RX PCM                                                   pull-up)     output                                          A2    Address 2 output                                                                           High (weak int                                                                              TDMed TX/RX PCM                                                   pull-up)     Input                                           A1    Address 1 output                                                                           Reserved. Do not                                                                            Reserved. Do                                                      connect.     not connect.                                    A0    Address 0 output                                                                           Mode select 0                                                                               Mode select 0                                                     (tie to Vss) (tie to Vss)                                    SCLK  Serial Port clock                                                                          Serial Port  Serial Port                                           out or PCM clock                                                                           clock only   clock only                                            out                                                                      SDIN  Serial Port data in                                                                        Serial Port data                                                                            Serial Port                                           or PCM data in                                                                             in only      data in only                                    SDOUT Serial Port data                                                                           Seial Port data                                                                             Serial Port                                           out or PCM data                                                                            out only     data out only                                         out                                                                      ______________________________________                                    

Referring again to FIG. 3, an example is shown of utilizing, in the preferred embodiment, the port paths provided by the transcoder 102 and the codec 101 by an external DSP 130. In the embodiment, the external DSP 130 processes the diverted signals (data) to provide an intercom or handset hands-free only operation. The external DSP 130 is physically connected to the controller 10 in the following manner: the CLK8K signal 110 (via pin BDP3₋₋ OUT5) is connected to interrupt control (INT) 128. The PCMCLK signal 108 is connected to slave clock (SCLK) 120, Synchronization of receive (R) pin 124 and transmit (T) pin 126 is coordinated by connecting the strobe output 106 to RT Sync 122. Pin R 124 is connected to pin A3 103 in order to receive and process diverted data (signals). Pin T 126 is connected to Pin A2 104 so that processed data from the external DSP 112 can be transmitted to either the transcoder 102 or the codec 101.

Numerous modifications and variations of the embodiments and, in particular, the preferred embodiments of the invention are possible in light of the teachings herein. For example, although the description has disclosed the use of an array of transistors in one possible embodiment of a ROM core, other transistor arrays or other arrangements may be used in other devices, such as, for example, a PLA, or the like. Each of these modifications and variations are intended to be included in the description herein and form a part of the present invention. The foregoing detailed description is, thus, to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims. 

What is claimed is:
 1. A system for selectively enabling intermediate data processing of digital signals external to an integrated circuit (IC), said system comprising:a transcoder; a codec connected to said transcoder; a data processor located externally to said IC; means for selectively diverting said digital signals, transmitted between said transcoder and said codec, to the external data processor for external processing of said digital signals; and means for returning the externally processed digital signals to said IC.
 2. The system for selectively enabling intermediate data processing external to the IC of claim 1 wherein said means for selectively diverting said digital signals to said external data processor includes:a programmable switch which diverts said digital signals in response to a strobe signal; a data path from said IC to said external processor; and means for formatting said digital signals for processing by the external processor.
 3. The system for selectively enabling intermediate data processing external to the IC of claim 2 wherein said means for returning said externally processed digital signals to said IC includes:a data path from said external processor to said IC; and means for formatting said digital signals for further processing by said IC. 